1. Field of the Invention
The present invention relates to a wavelength division multiplexing optical transmission system, having an optical amplifier, for transmitting multiple-wavelength signal light.
2. Related Background Art
From social needs at the advent of highly information-oriented society, research and development related to large-capacity, high-speed communications such as image communications, and long-distance communications such as international communications, using optical fiber transmission systems, are in vogue. Here, wavelength division multiplexing (WDM) transmission systems, which carry out high-speed, large-capacity optical communications by transmitting multiple-wavelength signal light (a plurality of signal light components having wavelengths different from each other) through optical fiber lines, have been under research and development as those responding to the rapid increase in demands for communications due to the Internet and the like in recent years.
Such a wavelength division multiplexing transmission system uses an optical amplifier such as an erbium-doped fiber amplifier (EDFA) in order to compensate for the transmission loss incurred upon transmitting multiple-wavelength signal light over a long distance. In the optical amplifier, pumping light having a predetermined wavelength is supplied to a silica type optical waveguide doped with a rare-earth element such as Er mentioned above, Pr, or Nd (e.g., erbium-doped fiber; EDF), the signal light fed into this optical waveguide is optically amplified, and thus amplified signal light is outputted. Semiconductor optical amplifiers and the like are also employed as the optical amplifier.